1. Field of Invention
The present invention relates to a multiple channel earphone, and more particularly to a multiple channel earphone with extended sound field and adjusting holes.
2. Description of Related Art
Our daily lives have been digitalized along with the development of digital technology. For example, digital video disc (referred as DVD generally) player has become a common video playing apparatus in our homes. Since the DVD player has Dolby Digital or Digital Theater System (DTS) decoding function, it can be used for decoding digital signals and output analog signals to speakers.
To obtain high quality digital video entertainment, multiple channel speakers are the necessary equipments, and 5.1 channel speakers are the basic multiple channel speakers.
FIG. 1 is a diagram of a home theater system with 5.1 channel speakers. Referring to FIG. 1, while the DVD player 100 is playing a video program, different sound signals are respectively output to a front left speaker 102a, a front right speaker 102b, a center speaker 104, a surround left speaker 106a, a surround right speaker 106b and a subwoofer speaker 108 to produce 3-D (three dimension) sound effect and high fidelity.
However, earphones have to be used while it's not suitable for playing sound through speakers (for example, which may disturb others). Referring to FIG. 2A, in general, the user of an earphone cannot enjoy multiple channel sound effect output from the DVD player since only one speaker 210 is disposed at both sides of the earphone 200a. 
Thus, a conventional earphone having a plurality of internal speakers is provided, as shown in FIG. 2B. A front speaker 202, a center speaker 204, and a surround speaker 206 are disposed at each side of the earphone 200b, and with a specially designed plug 208, the sound signals of different channels can be output by the DVD player to different speakers through the plug 208. The sound effect of the 5.1 channel speakers in the home theater system as shown in FIG. 1 can be produced. In the conventional earphone 200b, the delay of the output sound signals can be controlled digitally (for example, through circuit design), however, the output sound field is not ideal compared to the 5.1 channel speakers in the home theater system as shown in FIG. 1, therefore, the quality and performance of the multiple channel surround sound effect cannot be achieved.